Hi,
I can add a little more detail. This cam is connected to the link from the Throttle controls. It is, as it is stamped, particular to the engine and aircraft type, because it matches the profile of the desired engine and propeller combination. The two arrows at the left above the DB letters are the 2800 and 2600 rpm settings. The two arrows on the right side are the throttle fully closed range. These alloy cams seem to survive quite well because they are anodised. However, the bracket they fix on is lightweight and is usually mashed in a crashed engine in the ground. The speeder-cup type governor that these fit on is magnesium and, it is almost always corroded away, so, it is rare.
Cheers
Eng